One of the UK’s biggest trade unions, GMB, is staging an attack on online retailer Amazon tomorrow with demonstrations planned outside of its nine distribution depots.

Union GMB is plotting the demos to bring to account the online retailer, which despite causing controversy over tax avoidance, pays its staff just £6.20 an hour, a penny above the legal minimum.

The union is also planning to hand bosses at Amazon’s distribution centres mocked up ‘Asbos’, according to The Sun.

The Asbos claim that the etailer “knowingly underpaid corporation tax in the UK” and demand it should repay the money it owes and commit to paying normal levels of tax in the future.

GMB national organiser Paul Clarke told The Sun staff felt scared to speak out about working conditions, and added: “Our members at the company say the name Amazon has become a dirty word among friends and family. While everyone wants goods as cheap as possible, it’s now beginning to dawn on people the consequences of buying from tax-dodging companies who treat their staff so badly.”

Amazon found itself at the centre of a tax avoidance controversy last year and it was forced, alongside Google and Starbucks, to appear in front of MPs to explain why it had not paid any corporation tax despite generating £3bn in the UK in 2010.